Tek 2465 Battery

[SirCVH]

Hello
I was able to purchase a 2465DVS for $100, so I'm pretty excited as it is a whole lot more machine than I thought I'd be able to afford.  I have a question that I haven't been able to figure out and hopefully someone here can point me in the right direction.

On boot, the test routine returns a failure at Test 04 Number 19, which is an error for the EAROM, and I believe the manual says the description for 19 is a checksum error.  Everything seems to work well with the scope, and I can calibrate it and it works well, but the trace loses its position when the unit is turned off then on again.

I am working under the assumption that the battery needs replacement as I have read about, but I cannot find the battery anywhere for the EAROM on the board or in the schematics.  (It doesn't have the newer dallas nvram chips)  I have taken the whole thing apart and there are A LOT of boards in this sucker, but can't find anything that looks to me like a battery.

1.  Is my assumption to change the battery the correct route you would try?
2.  Where is the battery?  (Does the unit even have a backup battery?)
3.  Any suggestions on a replacement part?
4.  What is the process for swapping it out?  Will I need to get an extra battery or power supply to hook up to the earom while I desolder/resolder the permanent battery?


Thanks for any help, and let me know if any other info would be helpful!

[nanofrog]

Pics of where it's located: https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg74321/#msg74321

Replacement Battery: http://www.alliedelec.com/search/productdetail.aspx?SKU=70141129 (not sure if this is the least expensive source, but they do sell singles)

Hope this helps. 

[rf-loop]

If there read EAROM it is (mostly) EAROM. Not RAM with external battery and not NVRAM with internal battery.

Tektronix have used EAROM's, CMOS RAM with external  battery and NVRAM (CMOS RAM with battery and internal logic) in various models / versions.
 
It is possible that EAROM itself is bad but also it is good to check other things related to this.


Just one mutual extra suspect: Also, but not perhaps just this model/version, some models need enough power for complete all shut down processes after power off when it store "last state" for next power up (power supply).

[edavid]

Pics of where it's located: https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg74321/#msg74321

Replacement Battery: http://www.alliedelec.com/search/productdetail.aspx?SKU=70141129 (not sure if this is the least expensive source, but they do sell singles)

Hope this helps. 

Nope, doesn't help since it's the wrong model

Just one mutual extra suspect: Also, but not perhaps just this model/version, some models need enough power for complete all shut down processes after power off when it store "last state" for next power up (power supply).

The 2465 doesn't do this (try to store anything to EAROM during power down).

[SirCVH]

@nanofrog: Thanks for posting, as the other guys mentioned this model has EAROM instead of EPROM with battery.

@rf-loop: Thank you for the background and confirming that I'm not crazy, there just isn't a battery.  I was kind of hoping there was, because then I would know where to start troubleshooting.

What would be your first steps in troubleshooting?  I'm pretty new to this stuff...
Would you replace the EAROM right off the bat?  If so, what is the process?
With the comment about having enough shutdown power to store settings, is this the reason people change old caps on the power supply?

Thanks for any help anyone can provide!

[rf-loop]

Just one mutual extra suspect: Also, but not perhaps just this model/version, some models need enough power for complete all shut down processes after power off when it store "last state" for next power up (power supply).

The 2465 doesn't do this.

Tektronix 2465 service manual detail sample.  (models what have EAROM)
(also related to this EAROM  there is more information and also for power down (unexpected or user made)  "landing")

[SirCVH]

I found an old comment in the yahoo tek forum of a guy with a 2465 with the same error that I have.  He went through his power supply and found that bad caps were limiting power to the EAROM, and replacing the caps eliminated the error and some display issues he was having.  I am going to start going through the power supply tonight, and hopefully with my limited skills I can figure out replacement parts for the larger storage caps.  This could also address the issues with shutdown power that rf-loop is referring to.

If anyone has any input/ideas/suggestions I really appreciate it, I don't know much about this stuff yet.  Goal number one is to not shock the hell out of myself testing stuff on the PS, haha.